Fuel injection cranking signal modifying device



D. D. STOLTMAN Filed May 19, 1958 INVENTOR. 00/10/47 0 J/of/wan Jan. 26, 1960 FUEL INJECTION CRANKING SIGNAL MODIFYING DEVICE ATTORNEY United States Patent FUEL INJECTION CRANKING SIGNAL MODIFYING DEVICE Donald D. Stoltman, Henrietta, N.Y., assignor to General Motors Corporation, Detroit, Micln, a corporation of Delaware Application May 19, 1958, Serial No. 736,318

6 Claims. (Cl. 261-69) The present invention relates to a device for creating or supplementing thevacuum control force for a mass air flow type fuel injection system under engine cranking. More specifically, the present device is an improvement over the cranking enrichment mechanism shown lll copending application Serial No. 591,889, Dolza, filed June 18, 1956.

In the earlier system of the aforenoted copending application, a solenoid device was utilized which acted directly upon the fuel metering valve to increase the nozzle fuel flow under engine starting conditions. This previous device also recognized the insufficiency of the metering signal during engine cranking conditions. However, the earlier device was considerably more expensive than the present mechanism and further was operative during closed throttle cranking irrespective of the magnitude of the fuel requirement of the engine.

In the present device, a diaphragm actuated valve is provided which is opened by gravity or a spring force in such a way as to communicate the induction passage posteriorly of the throttle valve with a conduit leading from the throat of an induction passage venturi whereby manifold vacuum will supplement the venturi vacuum force when the combined venturi and manifold vacuum forces on the diaphragm is less than a given amount, e.g., two inches of water differential across the diaphragm. At such time as sufiicient air flow takes place through the induction passage as to increase the vacuum signal above said given value, the complementary action of venturi and manifold vacuum will close the diaphragm controlled valve thereby blocking further supplemental manifold vacuum from reaching the fuel metering valve controlling diaphragm.

Further objects and advantages of the present device will be apparent from a perusal of the detailed description which follows.

The drawing is a diagrammatic representation of a fuel injection system embodying the present invention.

As already noted, the present invention may 'be incorporated with a fuel injection system of the type shown in the aforenoted copending Dolza application, therefore, such system will be described only insofar as is necessary to an understanding of the present invention.

An air intake casing is provided at 10 and includes an induction passage 12 having a venturi 14 formed therein. A t-hrottle valve 16 is disposed in passage 12 posteriorly of venturi 14. An annular chamber 18 is formed about the throat of venturi 14 and radially inwardly communicates with the venturi throat whereby a vacuum force proportional to induction passage air flow is created in said chamber. Chamber 18 in turn communicates through a conduit 20 and a branch conduit 22 with a fuel metering valve control mechanism indicated generally at 23. Mechanism 23 includes a casing member 24 cooperating with a diaphragm 26 to define a vacuum chamber 28. A T-plug 30 is mountedon casing 24 and communicates at one side with venturi vacuum conduit 2,922,630 Patented Jan. 26, 1960 22 and at the other side with a conduit 32. As set forth in detail in the Dolza application, diaphragm 26 through a linkage mechanism 27 controls a fuel metering valve 29 which controls the metering pressure of fuel to fuel nozzles, not shown.

As described in copending application Serial No. 608, 797, Olson, filed September 10, 1956, now Patent No. 2,873,732, dated February 17, 1959, conduit 32 communicates with a U-shaped passage 34 which terminates in induction passage ports 36 and 38 anteriorly and posteriorly of the closed throttle 16. Passage 34 and conduit 32 are provided for the purpose of reinforcing or increasing the vacuum metering signal in chamber 28 during idle and off-idle conditions when the air flow through venturi 14 is too low to provide a suitable vacuum metering force.

An engine cranking signal valve mechanism is shown generally at 40 and includes a pair of casing members 42 and 44 peripherally clamping a diaphragm member 46 therebetween. Casing 44 includes a port 48 therein which communicates a chamber 50 defined by the casing and diaphragm 46'with the atmosphere. Port 48 is preferably a restricted hole, e.g., .020" diameter for the purpose of dampening diaphragm surging and preventing diaphragm vibration on boss 62 which otherwise generates objectionable noise.

Casing 42 includes ports 52 and 54. Port 54 communicates with a conduit 56 which branches off of venturi vacuum conduit 20. Port 52 communicates with a conduit 58 which connects at its other end with a port 60 formed in casing 10 and communicating with induction passage 12 posteriorly of throttle 16 to transmit manifold vacuum to conduit 58.

Casing 42 includes a downwardly opening boss or valve seat 62 formed about port 54 to define a vacuum chamber 64. A reinforcing washer-like member 66 is suitably fiXed to diaphragm 46 and disposed opposite port 52 and chamber 64.

Under normal conditions with the engine running, the manifold vacuum in conduit 58 acting through chamber 64 on diaphragm 46 as well as venturi vacuum in chamber 68 acting on the diaphragm will overcome the weight of the member 66 causing the diaphragm to seat against boss 62 to block communication of manifold vacuum with chamber 68. Under this condition no vacuum from the modifying device will be admitted to metering diaphragm chamber 28 to control actuation of the fuel metering valve 29.

However, with engine inoperative, the Weight of member 66 will cause diaphragm 46 to uncover seat 62 to communicate conduits 56 and 58. In this condition cranking vacuum posteriorly of throttle 16 will be transmitted to metering diaphragm chamber 28 to supplement the weak venturi signal in controlling diaphragm 26. In this way a sufiiciently strong vacuum control force is imposed on diaphragm 26 to insure an adequate supply of fuel will be metered to the engine by valve 29 for start ing purposes.

It is apparent that by suitably selecting the weight of member 66 as well as the areas of diaphragm 46 exposed to venturi and manifold vacuum, the enrichment device 40 can be made to function at any condition desired. As already noted, in the present instance it is only intended to render device 40 operative during cranking conditions. Accordingly, the area of diaphragm 46 and weight of member 66 are calculated to be overcome and block seat 62 when induction air passage air flow reaches a given value. To illustrate, it has been found that a vacuum force equal to two inches of water is the maximum required for cranking fuel flow through the fuel metering valve 29. Therefore, diaphragm area and memher 66 weight are of such that when the total vacuum force in chambers 64 and 68 exceed two inches of water the diaphragm will be moved upwardly closing port 52 and thereby blocking manifold vacuum from communi' cation with chamber 68 whereby fuel flow will be controlled solely in accordance with the air flow induced vacuum force in conduits 20 and 32.

I claim:

1. A charge forming device for an internal combustion engine comprising an air induction passage, a venturi formed in said passage, a throttle valve disposed in said passage posteriorly of said venturi, a fuel metering mechanism including a diaphragm member, conduit means communicating said venturi with said diaphragm permitting a vacuum force proportional to air flow to act on said diaphragm and thereby control the quantity of fuel flow through said mechanism, and a metering vacuum modifying means connected between said air induction passage and said fuel metering mechanism and comprising a pressure responsive valve mechanism, a first port in said metering means adapted to be controlled by said valve mechanism, a second conduit means communicating said port with said induction passage posteriorly of said throttle valve whereby said valve mechanism is exposed to manifold vacuum, a second port in said metering means, said conduitnmeans Communicating said venturi with said diaphragm also communicating with said second port, the total vacuum force acting on said valve mechanism during normal engine operation blocking communication between said first and second ports, said valve mechanism being adapted to communicate said ports when said total vacuum force falls below a predetermined value whereby manifold vacuum supplements venturi vacuum to control said fuel metering diaphragm.

2. A charge forming device as set forth in claim 1 in which said metering vacuum modifying device comprises a pair of easing members, a diaphragm peripherally clamped between said members and coacting therewith to define first and second chambers, said first and second ports being formed in one of Said casing members and communicating with said first chamber, the second chamber being exposed to atmospheric pressure.

3. A charge forming device as set forth in claim 2 in which said pressure responsive valve mechanism includes a valve seat formed about said first port, a weighted element mounted on the vacuum modifying device diaphragm, said element being aligned with said valve seat and coacting with said latter diaphragm to control flow through said first port.

4. A charge forming device as Set forth in claim 3 in which the area of the vacuum modifying device diaphragm exposed to manifold and venturi vacuum forces and the weighted element coact to uncover said valve seat by gravity actuation when air flow through the induction passage falls below a predetermined value.

5. A charge forming device as set forth in claim 3 in which said first port and said weighted element are centrally disposed relative to the associated diaphragm and casing members.

6. A charge forming device as set forth in claim 3 in which said valve seat comprises an open ended cylindrical portion dependingfrom said one casing member and further in which said weighted element is diametrically coextensive with said cylindrical portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,751,201 Heftler June 19,1956 

